/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.instrument.classloading;

import java.lang.instrument.ClassFileTransformer;

import org.springframework.core.OverridingClassLoader;
import org.springframework.lang.Nullable;

/**
 * Simplistic implementation of an instrumentable {@code ClassLoader}.
 *
 * <p>Usable in tests and standalone environments.
 *
 * @author Rod Johnson
 * @author Costin Leau
 * @since 2.0
 */
public class SimpleInstrumentableClassLoader extends OverridingClassLoader {

    static {
        ClassLoader.registerAsParallelCapable();
    }


    private final WeavingTransformer weavingTransformer;


    /**
     * Create a new SimpleInstrumentableClassLoader for the given ClassLoader.
     *
     * @param parent the ClassLoader to build an instrumentable ClassLoader for
     */
    public SimpleInstrumentableClassLoader(@Nullable ClassLoader parent) {
        super(parent);
        this.weavingTransformer = new WeavingTransformer(parent);
    }


    /**
     * Add a {@link ClassFileTransformer} to be applied by this ClassLoader.
     *
     * @param transformer the {@link ClassFileTransformer} to register
     */
    public void addTransformer(ClassFileTransformer transformer) {
        this.weavingTransformer.addTransformer(transformer);
    }


    @Override
    protected byte[] transformIfNecessary(String name, byte[] bytes) {
        return this.weavingTransformer.transformIfNecessary(name, bytes);
    }

}
